Editors’ Highlights

Carbonate Melting Enhances Mantle CO2 Fluxes in Old Ocean Basins

The amount of CO2 segregated from the mantle by carbonate melting beneath old oceanic crust may equal that emitted along the mid-ocean ridge system, thereby contributing to the global carbon cycle.

Source:
Geophysical Research Letters

Map of the flux of CO2 segregated from the mantle by carbonate melting. While CO2 fluxes are highest at mid-ocean ridges, low-degree melting occurs over large areas away from the ridge axes and contributes a significant fraction of CO2 to the total segregation flux. Melting is not predicted in areas where the mantle is downwelling (gray); melting beneath the continents (purple) is not estimated. Credit: Clerc et al., 2018, Figure 1c

The birth of new ocean crust along the mid-ocean ridge system releases a significant amount of carbon dioxide (CO2) gas as part of the global carbon cycle. By integrating models of mantle convection with petrologic data for carbonate melting, Clerc et al. [2018] predict pervasive carbonate melting beneath old oceanic crust across the ocean basins. Including carbonate melting, the study correctly predicts the thickness of ocean crust produced at ridge axes and suggests that off-axis melting generates an additional volume of melt that is greater than the global volume of all seamounts found away from hot spots. Carbonate melting away from the mid-ocean ridges may contribute an additional flux of CO2 from the mantle comparable to the flux produced by ridge volcanism, suggesting a previously overlooked source of CO2 in the global carbon cycle.

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